Nutrient - Flax Oil

Its place in a healthy diet

By Karen Wilson BSc (Hons) MSC Nut Med

Anyone who heard Radio 4’s Food Programme in October 09 will have been horrified to hear Alex Richardson’s statement ‘flax will do nothing for anybody. Conversion (to EPA/DHA) is abysmal… Don’t waste your money on them’. As she is not a nutritional expert, but a psychologist interested in brain function, it is hardly surprising that her knowledge and research relates to the effects of EPA and DHA on brain-related disorders.

The clinical data identifies alpha linolenic acid as an important dietary factor in optimising health. All the evidence suggests that Omega 3s from plants have an important health function, particularly in cell membranes and cardiovascular health, but also as a precursor to the much-researched polyunsaturated fatty acids EPA and DHA.

The real messages from the programme were to eat more Omega 3 and less Omega 6, as the ratio of these two important nutrient groups is the key to optimal good health, and to beware processed foods claiming to be high in Omega 3, such as margarine, as the labelling may mislead.

The reason this programme was aired in the first place was probably because of ill-thought-out regulations on food labelling, which the EU are trying to push through at present. There has been uproar in academic circles, with key experts writing to the regulators voicing their concern that people will be hoodwinked into thinking that processed foods like margarine are a rich source of health-giving Omega 3s.

You can see why there is such a furore among people who know about nutrition. As the programme identified, it will allow margarine and other processed foods to claim ‘high in Omega 3’ when, in reality, there is hardly any Omega 3 present.

Earlier in the broadcast, they discussed the ratio between Omega 3 and Omega 6. The overwhelming increase in Omega 6 is one of the biggest dietary changes in the Western world and is of great concern to nutrition experts. Professor Crawford, a leading expert in Omega 3s and health from London Metropolitan University, is convinced that the current ratio of 10:1 Omega 6 to Omega 3 in the diet is a major cause of many of the ‘diseases of civilisation’ and the cause of most inflammatory disease. He urges us all to bring that ratio down - in the brain, the ratio is closer to 1:1. An Australian researcher on the programme agreed, stating that high ratios of omega 6:3 are linked to obesity and homicide rates. This is thought to be due to an alteration in the speed of processing across membranes.

This is where ALA, the main Omega 3 component of flax oil, comes in. Eating flax seeds and flax seed oil will bring that all-important ratio of Omega 6 to 3 down to a healthier level. ALA is an essential fatty acid, which cannot be made in the body. It is converted ultimately to EPA and DHA, but the conversion rate was generally thought to be poor.

Excessive dietary linoleic acid depresses the activity of both omega 6 and omega 3 pathways, whereas low linoleic acid intake will raise their activity. Similarly, diets high in alpha linolenic acid and lower in linoleic acid can effect the conversion by shifting it in favour of the Omega 3 pathway1 – another good reason for altering the ratio of Omega 6:3 intake. Other dietary factors, such as trans fatty acids and types of protein, have been implicated in affecting the conversion, while vitamins and minerals act as co-factors. Omega 6s will also compete with Omega 3s for incorporation into cell membranes, where they effect membrane fluidity and the function of membrane-bound receptors and enzymes.

More recent evidence questions and refutes the long-held view that ALA is poorly converted to EPA. The FORCE study2 on the effects on EPA levels in plasma of people taking flax seed versus placebo showed that EPA levels increased by 60% in 6 weeks in the flax oil group. This was a double-blind, placebo-controlled study using 3g ALA per day in a group of chronically ill people with poor nutrition.

When flax seed oil was compared to fish oil in a study of US fire fighters3 (a group with known high risk of CVD), the fish oil produced a rapid increase in red blood cell DHA and total omega 3s. Flax oil also produced a significant increase, over 12 weeks, in EPA and DPA in red cells. The researchers concluded that an optimal dose was 1.2g fish oil compared to 2.4g flax oil daily.

What evidence is there to support supplementation with ALA from flax seed oil?

Early researchers found it difficult to establish a role for ALA other than as a precursor to EPA. In the absence of other Omega 3 PUFAs in the diet, they were able to show that a deficiency of ALA resulted in reduced levels of EPA, DHA and DPA in all tissues. However, early studies showed oxidation of ALA occurs readily and its carbon skeleton is recycled4. This suggested other roles for this essential nutrient.

More recent studies have shown that ALA has a positive impact on cardiovascular health, insulin resistance and may also have an antioxidant role. A recent review in Lipids in Health and Disease5 suggests that ALA has potent antioxidant and anti-cytotoxic roles, which are of possible significance in disease states such as diabetes, where oxidant stress is elevated.

In diabetes, ALA has a similar effect to both EPA and DHA, including up-regulation of insulin receptors and PPARs and down-regulation of NF-kB, but this effect tends to be less potent with ALA. The same review reports an overall protective effect on cardiac outcomes, not solely explained by the reductions seen in cholesterol levels. Further work is needed to fully understand the role of ALA in cardiac health.

Alpha linolenic acid and linoleic acid are also precursors of the biologically-active eicosanoids, which include prostaglandins (PG), thromboxanes and leukotrienes (LT). Eicosanoids are involved in a wide range of regulatory processes and most importantly in inflammation. 3-series PG and 5-series LT from ALA are less potent inflammatory agents than the 2-series PG and 4-series LT derived from arachidonic acid (AA - Omega 6). Because the typical Western diet contains much higher Omega 6 to Omega 3, the membranes of most cells contain large quantities of AA, which lends itself to metabolism to highly inflammatory prostaglandins of series 2 type5. Professor Crawford believes this to be the basic cause of the ‘diseases of civilisation’, including CVD.

Far from being a waste of money, both studies suggest that ALA from flax oil does, in fact, convert to longer chain EPA, if taken in adequate amounts, it just takes a little longer than supplementing directly with EPA. With fish stocks dwindling, flax oil and other Omega 3 plant oils will assume increasing importance in a healthy diet. The research shows that ALA has a key role to play in many areas of health.